The present invention relates to springs and spring assemblies for seating and bedding such as for example, mattresses and box-springs and although the invention is particularly suitable for mattresses and/or box-springs to be used in sofa beds, it will have applicability in other seating or bedding units and uses.
The present invention is an improvement to the springs and spring assemblies disclosed in U.S. Pat. No. 4,654,905 entitled "BODY SUPPORT FOR BED OR SEAT" and assigned to the assignee of the present application. The disclosure of the aforesaid U.S. Pat No. 4,654,905 is hereby incorporated by reference into the instant application as part hereof. The spring assembly referred to here is disclosed in FIGS. 12 and 13 of said U.S. Pat. No. 4,654,905 and includes a series of generally "M" shaped or sigma shaped springs linked together in chain-like fashion with each spring including upper and lower runs and an intermediate run with coils in the upper and lower runs and in the intermediate run. The upper and lower runs have hooked shaped portions which are received in the coils of the adjacent spring to interconnect the springs in chain like fashion. Each of the springs is made from spring wire material which is bent into the configuration described above. The individual springs are inter-connected as described to form a plurality of rows of springs. In addition, the rows are interconnected by wire runners which extend transversely of the rows of springs and have intermediate offset portions connected to the rows of springs at the upper runs thereof. The runners are shown at 75 in FIG. 13 of U.S. Pat. No. 4,654,905.
One of the advantages of the aforementioned spring assembly is that it can be moved between erect and retracted positions to increase or decrease the depth of the bedding or seating unit. This not only provides a great advantage in storage of the units, but also a great advantage in sofa beds since it allows a full size mattress to be incorporated in a sofa bed having a frame of conventional dimensions. The assemblies also provide enhanced body support and comfort in seating and bedding units.